The present invention relates to a leveling method and a leveling device to be used in a measuring equipment such as a surveying instrument.
When measurement is performed by using a measuring equipment, e.g. a surveying instrument, first of all, it is necessary to install the surveying instrument at horizontal condition, and the surveying instrument is provided with a leveling device to make the installing condition horizontal.
Referring to FIG. 4, brief description will be given below on a surveying instrument provided with a leveling device. The surveying instrument shown in FIG. 4 is a rotary laser device for forming a reference plane by projecting a laser beam by rotary irradiation.
The rotary laser device 1 comprises a casing 2 and a laser projector 4 with a projection light optical axis 3. The laser projector 4 is accommodated in the casing 2 and can be tilted in an arbitrary direction.
A rotating unit 5 is rotatably mounted on upper portion of the laser projector 4, and a pentagonal prism 6 is provided on the rotating unit 5.
A scanning gear 7 is mounted on the rotating unit 5, and a scanning motor 9 with a driving gear 8 is arranged on the laser projector 4. The rotating unit 5 is rotated and driven by the scanning motor 9 via the driving gear 8 and the scanning gear 7.
Within the casing 2, two sets of X-axis tilting mechanism 11 and Y-axis tilting mechanism (one of them is not shown) are arranged around the laser projector 4 with respect to X-axis and Y-axis respectively. The X-axis tilting mechanism 11 comprises an X-axis tilting motor 12, an X-axis tilting screw 13 with a rotation center in a direction parallel to the laser projector 4, and a sliding nut 14 screwed with the X-axis tilting screw 13. As the X-axis tilting motor 12, a motor able to control rotation angle, e.g. a stepping motor, is used.
The laser projector 4 comprises two tilting arms 15 (one of them is not shown) running perpendicularly to the projection light optical axis 3 and extending in horizontal direction. The two tilting arms 15 perpendicularly cross each other, and the tilting arm 15 is engaged with the sliding nut 14 via a pin.
The X-axis tilting motor 12 can rotate the X-axis tilting screw 13 via a driving gear 16 and a tilting gear 17. By rotation of the X-axis tilting screw 13, the sliding nut 14 is moved up or down. By moving up or down of the sliding nut 14, the tilting arm 15 is tilted, and the laser projector 4 is tilted.
Another set of the Y-axis tilting mechanism not shown in the figure can tilt the laser projector 4 in a direction perpendicularly crossing the tilting direction of the X-axis tilting mechanism 11 by the same procedure as the procedure of the X-axis tilting mechanism 11.
In a plane, which perpendicularly crosses the projection light optical axis 3, there are provided an X-axis tilt sensor 18 and a Y-axis tilt sensor 19. The X-axis tilt sensor 18 perpendicularly crosses the Y-axis tilt sensor 19 and runs in parallel to the tilting arm 15. By the X-axis tilt sensor 18 and the Y-axis tilt sensor 19, tilt angle of the laser projector 4 can be detected in an arbitrary direction. Based on the detection results of the X-axis tilt sensor 18 and the Y-axis tilt sensor 19, the laser projector 4 is tilted by two sets of the X-axis tilting mechanism 11 and the Y-axis tilting mechanism (one of them is not shown) via two tilting arms (one of them is not shown), and leveling can be performed so that the laser projector 4 is in vertical position and the laser projector 4 can be tilted at an arbitrary angle.
Under condition that the laser projector 4 is leveled in vertical position, a laser beam is emitted from the laser projector 4. The laser beam is deflected in horizontal direction by the pentagonal prism 6 and is projected in horizontal direction. The rotating unit 5 is rotated by the scanning motor 9 via the driving gear 8 and the scanning gear 7. By rotating the rotating unit 5, the laser beam is projected by rotary irradiation, and a horizontal reference plane is formed.
The X-axis tilting motor 12 rotates the X-axis tilting screw 13 by a predetermined rotation amount (a predetermined number of pulses) from the condition where the laser projector 4 is leveled once. And then, the laser projector 4 can be tilted at a predetermined angle. Under the condition where the laser projector 4 has tilted, by projecting the laser beam by rotary irradiation, a tilt reference plane is formed.
As described above, when a reference plane is formed by the rotary laser device 1, the rotary laser device 1 is leveled at first. Now, description will be given on a conventional leveling method by referring to FIG. 5.
FIG. 5 shows tilt angle and leveling time, in case that the tilt sensor is an optical type tilt sensor. A curve Q in FIG. 5 indicates a tilt angle of the optical type tilt sensor, and a curve S indicates an output signal of the optical type tilt sensor.
To simplify the explanation, description will be given below on the leveling relating to the X-axis tilt sensor 18.
The X-axis tilt sensor 18 is designed to detect a tilt angle by the position of an air bubble within a bubble tube filled with liquid. In this respect, response delay is caused by the movement of the air bubble when the X-axis tilt sensor 18 is tilted. Therefore, the response delay of the X-axis tilt sensor 18 must be taken into account in the leveling operation.
Also, in the X-axis tilt sensor 18, angle can be detected in a range of very small angle. However, if it is beyond the detection range, tilting direction can be detected but the tilt angle itself cannot be detected. As the X-axis tilt sensor 18 has these characteristics, the measurement is performed in two regions: a region of dynamic range where tilt angle can be measured, and the region beyond dynamic range where only tilting direction can be detected.
Specifically, as shown in FIG. 5, in the region beyond dynamic range, a direction, in which the X-axis tilt sensor 18 is tilted, is detected. And the rotary laser device 1 is tilted in a direction reverse to the direction detected by the X-axis tilting mechanism 11. Next, it is judged whether a target value (a preset and stored 0 value) of output signal of the X-axis tilt sensor 18 has been passed or not. When it is confirmed that the target value has been passed, tilting speed is decreased by the X-axis tilting mechanism 11, and the rotary laser device 1 is tilted so that tilting direction of the X-axis tilt sensor 18 is reversed. When it is again confirmed that the target value has been passed, the tilting speed is decreased further by the X-axis tilting mechanism 11, and the rotary laser device 1 is tilted so that the tilting direction of the X-axis tilt sensor 18 is reversed again. By repeating these procedures, it is possible to attenuate the region of dynamic range and to perform leveling of the rotary laser device 1 in horizontal direction.
Next, when the detected tilt angle is entered the region of dynamic range, the leveling operation is slowed down, and leveling is performed in horizontal direction so that hunting does not occur.
In the conventional leveling method as described above, the X-axis tilt sensor 18 is tilted so that the X-axis tilt sensor 18 passes through the target value (a preset and stored 0 value), and tilting direction of the X-axis tilt sensor 18 is repeatedly reversed each time horizontal direction (i.e. the target value) is passed through, and detection angle of the X-axis tilt sensor 18 is converged so that detection angle of the X-axis tilt sensor 18 is turned to 0 when entering the region of dynamic range. In this case, problem may arise that much time is required until the leveling operation is completed.